1. Technical Field
The invention relates to a variable length connecting rod, an effective length of which can be varied, and a variable compression ratio internal combustion engine including the variable length connecting rod.
2. Description of Related Art
An internal combustion engine including a variable compression ratio mechanism that can vary a mechanical compression ratio of the internal combustion engine has been known. Examples of the variable compression ratio mechanism include those that vary an effective length of a connecting rod used in the internal combustion engine (for example, Japanese Patent Application Publication No. 2011-196549, and International Publication No. WO2014/019683). The effective length of the connecting rod means a distance between the center of an opening that receives a crankpin and the center of an opening that receives a piston pin in the connecting rod. Therefore, when the effective length of the connecting rod is increased, a volume of a combustion chamber when a piston is at a compression top dead center is decreased, so that the mechanical compression ratio is increased. On the other hand, when the effective length of the connecting rod is decreased, the volume of the combustion chamber when the piston is at the compression top dead center is increased, so that the mechanical compression ratio is decreased.
A connecting rod in which an eccentric member (an eccentric arm or an eccentric sleeve) that can rotate with respect to a connecting rod body is provided at a small diameter end of the connecting rod body has been known as the variable length connecting rod, the effective length of which can be varied (for example, JP 2011-196549 A, and International Publication No. WO2014/019683). The eccentric member has an opening that receives a piston pin. The opening of the eccentric member is provided eccentrically from a rotational axis of the eccentric member. In the variable length connecting rod, when a rotational position of the eccentric member is changed, the effective length of the connecting rod can be correspondingly varied.